A combustor of a gas turbine is provided with a transition piece which supplies high-temperature and high-pressure gas to a turbine. This transition piece is provided with a trunk part formed in a cylindrical shape, and a flange which is provided at the downstream end of the trunk part, and which is to be connected to the first stage entry of the turbine.
The trunk part of a combustor in general is such that the cross-sectional area thereof becomes smaller and the flow velocity of combustion gas flowing thereinside increases with approach to the downstream side. Therefore, among the transition piece, with respect to the downstream end part of the trunk and the flange, heat transfer rate of the combustion gas increases. That is to say, among the transition piece, the downstream end part of the trunk part and the flange are exposed to the most thermally severe environment.
Consequently, in the transition piece disclosed in Patent Document 1, in order to cool the flange, there are formed cooling air passages which pass through this connecting flange.